HEADQUARTERS ARMY OF THE POTOMAC,
May 28, 1863.

Brigadier General A. PLEASONTON, Commanding Cavalry Corps:

GENERAL: I am directed by the major-general commanding to instruct you to dispatch, without delay, Brigadier-General Buford, with all of his available force, to Bealeton and vicinity, and for him, by virtue of his rank, to assume command of all the cavalry forces operating in that district of country. It is reported that the enemy's skirmishers have shown themselves on the north side of the Rappahannock, in the vicinity of Warrenton. If General Buford should find this to be the case, and to keep them there; or, if the should find himself with sufficient force, to drive the enemy out of his camp near Culpeper and across the Rapidan, destroying the bridge at that point. The advance of the enemy's cavalry in the vicinity of Warrenton may have had for its object a concealment of a movement in force up the Valley. The commanding general desires that no labor be spared to ascertain the true object of the movement. At all events, they have no business on this side of the river.

Please inform General Buford that he will draw his supplies by the Orange and Alexandria Railroad. Also that one division of the Fifth Corps has been ordered to relieve the cavalry pickets at Banks', United States, Richards', and Kelly's fords, and, when relieved, for the cavalry to report to Brigadier-General Gregg. The reserve infantry force has been directed to take post at Morrisville.

You will direct the senior cavalry officer of the Upper Rappahannock to keep headquarters advised of all your operations, as well as those of the enemy, by telegraph.

I am, very respectfully, your obedient servant,

S. WILLIAMS,

Assistant Adjutant-General.

HDQRS. CAVALRY CORPS, ARMY OF THE POTOMAC,
May 28, 1863.

Brigadier General JOHN BUFORD, Commanding Reserve Brigade, Dumfries:

Move, with all your available force and Elder's battery, to Bealeton; take command of the whole force at that point, and drive the rebel scouts and parties in the neighborhood of Warrenton and Sulphur Springs across the Rappahannock River.

Leave your dismounted men, under a good officer or two, at Dumfries.

General Meade will picket the Rappahannock to Kelly's Ford. His reserves will be at Morrisville. Draw in your pickets from that par of the river.

Answer by telegraph.

A. PLEASONTON,

Brigadier-General, Commanding Corps.

CIRCULAR.] HEADQUARTERS ARMY OF THE POTOMAC,

Camp near Falmouth, Va., May 28, 1863.

The First Division of the Fifth Army Corps has been directed to cover and defend Banks', United States, Richards', and Kelly's Fords, with a reserve at Morrisville.